Method of controlling metal thin film formation conditions

Abstract

Measurement of temperature - internal stress characteristics of an Al thin film formed on an Si substrate is performed. The amount of an impurity or impurities mixed in the thin f ilm can be obtained in accordance with the measured characteristics. A migration start temperature of Al atoms in the thin film in the characteristics obtained when the temperature is increased is fed back as information to the thin film formation step, thereby controlling an impurity amount in an atmosphere for forming the thin film.

What is claimed is: 
     
       1. A method of controlling formation conditions of a metal film to be formed on a substrate, comprising the steps of: forming a first metal film under first conditions including an impurity amount in a formation atmosphere;   measuring temperature-internal stress characteristics of the first metal film;   deriving from the characteristics a migration start temperature of atoms constituting the first metal film; and   adjusting the impurity amount in the formation atmosphere on the basis of a deviation of the migration start temperature from a reference temperature, when forming in the formation atmosphere a second metal film which has substantially the same composition as that of the first metal film.   
     
     
       2. The method according to claim 1 wherein the reference temperature is determined by the steps of: forming individually a plurality of metal films, each of which has substantially the same composition as that of the first metal film, under the first conditions except that the metal films are formed by use of different impurity amounts in the formation atmosphere;   measuring temperature-internal stress characteristics of each of the metal films;   deriving from the characteristics of each of the metal films a migration start temperature of atoms constituting each of the metal films;   measuring a relationship between the migration start temperatures and durability of the metal films; and selecting the reference temperature on the basis of durability required of the second film.   
     
     
       3. The method according to claim 2, wherein the durability of each of the metal films is determined in terms of MTTF values obtained in a disconnection stress migration test. 
     
     
       4. The method according to claim 2, wherein each of the migration start temperatures is derived from the temperature-internal stress characteristics when a temperature is increased. 
     
     
       5. The method according to claim 4, wherein the impurity amount in the formation atmosphere of the second metal film is set lower than that of the first metal film when the migration start temperature of the first metal film is higher than the reference temperature. 
     
     
       6. The method according to claim 5, wherein the impurity amount is an amount of impurities comprising H 2  O, N 2 , O 2 , and CO. 
     
     
       7. The method according to claim 6, wherein each of the metal films is formed by a sputtering method. 
     
     
       8. The method according to claim 7, wherein the substrate is a semiconductor substrate and each of the metal films is formed of a conductive material. 
     
     
       9. The method according to claim 8, wherein the conductive material is a conductive material selected from the group consisting of W, Mo, Ti, Ta, and Zr, silicides thereof, Al, and Al alloys. 
     
     
       10. The method according to claim 8, wherein the conductive material is Al.